Kim Sengupta: Air power is essential to defeat Taliban, but so is local support

The decision by the US to send a senior officer to Afghanistan in connection with the investigation into the air attack reflects the seriousness with which the American authorities are being forced to treat this latest killing of civilians. The lethal "collateral damage" caused by air strikes has been the source of deep anger among Afghans and has led to demands from President Hamid Karzai for Western forces to change their tactics to prevent civilian casualties.

But sheer lack of US and Nato manpower on the ground means warplanes play a central role in operations and in bailing their forces out in emergencies. Air power, increasingly unmanned drones, are also vital in carrying out attacks on the Taliban across the Pakistan border. But some countries in the coalition have been taking steps to cut down on civilian casualties. The Danish battlegroup, which operates alongside British forces in Helmand, brought in Leopard tanks because, it was felt, ground fire would be more accurate than air attacks and reduce "accidents".

The Canadians, too, have deployed German-made Leopards which has made them less reliant on calling in warplanes. The American military is said to have been opposed to the introduction of the tanks because it believed it would lead to an escalation of the conflict with the Taliban and their allies replicating the Iraq scenario by escalating the use of explosive devices to counter the tanks.

In the end, practical necessity may lead to the Western military taking a more cautious approach to air strikes. Security in Afghanistan is steadily deteriorating and the US and Nato can ill afford to fuel the discontent as women and children are killed "by mistake". The government of President Karzai is also in a precarious position and, with elections looming, the killings are undermining his authority. Mr Karzai has called for a review of air attacks by Nato and an updated "status of forces" agreement between his government and Western military. The latest deaths, say Afghan officials, may force a deadline for these to be concluded.